In some scenarios, the plans are less expensive than Verizon's Share Everything

AT&T announced voluntary wireless data sharing plans on Wednesday that don't require new and current customers to enroll, a marked distinction from the Verizon Wireless' forced Share Everything plans for new and upgrading customers. The Verizon plans took effect last month.

AT&T didn't specify a starting date for its Mobile Share plans, saying they will be available in late August to both consumers and business customers. AT&T made the explicit point in a statement that "current customers are not required to switch to the new plans, but can choose to do so without a contract extension."

AT&T's plans have been under evaluation for months as part of an overall industry effort to find ways to charge for data usage as young customers lessen the demand for voice networks.

A spokesman for AT&T refused to comment on Verizon's sharing plans or whether AT&T is setting up a voluntary plan in reaction to Verizon's approach. Verizon customers strongly criticized the plans when they were first announced, although a Verizon spokeswoman said customer response has been generally positive since they rolled out.

AT&T also said Wednesday that it would not change its device upgrade policies. Verizon's Share Everything plans allow unlimited data users to use an older phone or a more expensive unlocked phone. But if they buy a new subsidized-price phone, they have to convert to the Share Everything plan.

"I have no doubt that AT&T studied the Verizon plans closely and took all the feedback and controversy [with Verizon] into consideration," said Jack Gold, an analyst at J. Gold Associates. "AT&T's plan is a more open environment, as you can keep the old plan, but it is still not inexpensive."

Like Verizon, AT&T has set up data sharing across up to 10 devices, with unlimited domestic calling and texting provided. Under the voluntary shared plans from AT&T, users will pay between $30 and $45 a month for each smartphone or mobile device used, and a separate fee depending on how much data they select. But -- unlike Verizon -- the monthly device charge for smartphones drops as the monthly data allowance increases.

With AT&T Mobile Share, 1GB of shared data will cost $40, plus $45 for each smartphone. The plans step up from there in six tiers to 20GB of data per month for $200, and device charges of $30 each. The cost per month for basic phones in shared AT&T plans will be $30; for laptops and laptop modems, $20; and for tablets and gaming devices, $10.

Today with AT&T, individual consumer tablet customers can buy 3GB of data for $30 a month, compared to the Mobile Share cost of $40 per month for 1 GB. Today, business customers with AT&T can buy data for various devices for $45 a month for 3GB.

Mark Siegel, an AT&T spokesman, said those current individual rates will remain available to consumers and business customers, and both groups will have the option of sharing data across up to 10 devices at the new rates.